Experimental comparison of caudal wedge ostectomy to cranial wedge ostectomy for surgical treatment of overriding/impinging spinous processes in horses

Abstract

Background

Caudal wedge ostectomy has not been investigated for overriding or impinging spinous processes (SPs).

Objectives

To establish the feasibility of caudal wedge ostectomy and compare measures of surgical trauma and error between hypothetical caudal and cranial wedge ostectomies on SPs of different inclinations.

Study Design

Experimental, method comparison study.

Methods

Computed tomography and caudal wedge ostectomy surgery were performed on four cadavers. Observations, technical difficulties, and surgical errors were recorded. Radiographs from 67 horses with overriding/impinging SPs were reviewed. Hypothetical ‘ideal’ caudal and cranial wedge ostectomies, and ‘error’ ostectomies 12° from ideal, were drawn at sites of impingement. Ostectomy area/SP width, ostectomy length/SP width, absolute difference of exit angles (angle ostectomy exits the SP) from 90°, and number of error ostectomies failing to exit the SP (never-ending-cuts [NEC]) were calculated. Continuous variables were compared between techniques in caudally and cranially inclined SP groups using Wilcoxon signed-rank tests. Proportions of NEC were compared using McNemar's tests.

Results

No surgical errors were recorded with caudal wedge ostectomy. Median ostectomy area/SP width was lower for caudal versus cranial wedge ostectomy in caudally (14.32, interquartile-range [IQR] 9.72–20.34 vs. 25.57, IQR 17.74–33.06; p < 0.001) and cranially inclined SP groups (11.78, IQR 7.98–17.19 vs. 19.62, IQR 13.65–28.68; p < 0.001). Median difference in exit angles from 90° was smaller for caudal versus cranial wedge ostectomies in caudally (34.77°, IQR 26.85°–45.91° vs. 67.54°, IQR 58.13°–74.55°; p < 0.001) and cranially inclined SP groups (49.14°, IQR 35.61°–59.33° vs. 62.84°, IQR 55.34°–70.61°; p < 0.001). The proportion of NEC was lower for caudal versus cranial wedge ostectomy in caudally (37.6%, 95% confidence interval [CI] 29.4%–45.8%; n = 50/133 vs. 96.2%, 95% CI 93.0%–99.5%; n = 128/133; p < 0.001), but not in cranially inclined SP groups (76.8%, 95% CI 70.9%–82.7%; n = 152/198 vs. 84.3%, 95% CI 79.3%–89.4%, n = 167/198; p = 0.06).

Main Limitations

Potential bias drawing ‘ideal’ ostectomy.

Conclusions

Experimentally, caudal wedge ostectomy was feasible, removed less bone, and resulted in fewer NEC in caudally inclined SPs. Further investigation of the technique is warranted.